The transmission of light and images through bundles comprised of flexible or adjacently fused optical fibers is an established art. Image conduits such as inverters, tapers and “straight-throughs” are well known to practitioners of the optical fiber arts. Fused optical fiber image conduits find broad application as components in such devices as night visions goggles, rifle scopes, x-ray detectors and medical imaging apparatus, by way of non-limiting example.
Various existing imaging devices incorporate optical fiber components coupled with image detector arrays such as charge-coupled devices (CCDs) and complimentary metal-oxide semiconductor (CMOS) circuits. Fundamental to each of these devices is the optical coupling of the optical fiber component with the image detector array such that an image introduced into a first end of the optical fiber component is transmitted through the optical fiber component for registration by the image detector array. Among the fused optical fiber components currently coupled with image detector arrays are tapered bundles (tapers) that either reduce or enlarge an input image, depending on whether the small or large end is regarded as the input end; elongated “straight-through” bundles that neither reduce nor enlarge an image; and optical fiber faceplates that neither reduce nor enlarge an inputted image.
Two or more traditional optical fiber faceplates (hereinafter “faceplate”), each of which is coupled to a corresponding detector array, can be mutually abutted in order to form a larger-format tiled imaging array. However, because the dimensions or “footprint” of each faceplate must match the footprint of its corresponding detector array in order to avoid gaps in the input image, the ability to tile multiple traditional faceplates is limited due to the need to route electrical conduits (e.g. bond wires) to and from the image detector array corresponding to each faceplate. For instance, while a 2×N array of tiled faceplate/detector-array pairs is feasible by orienting the detector arrays such that their electrical conduits lead out to the perimeter of the tiled array, arrays 3×3 and larger are unwieldy because of the difficulties associated with routing electrical conduits to the interior (non-peripheral) detector array(s).
In order to overcome the difficulties associated with tiling faceplates and their associated detector arrays in order to form large format imaging arrays, traditional reducing tapers of square or rectangular cross-section can be used in place of traditional faceplates. However, as is known in the art, the cross-sectional area of a traditional taper changes quite gradually as a function of length. Accordingly, the reduction in cross-sectional area necessary to have the larger image-input ends mutually abutted while the smaller image-output ends are sufficiently spaced apart to accommodate electrical conduits indicates tapers substantially thicker than a faceplate between the image-input and image-output ends. The use of relatively thick tapers in place of faceplates, while alleviating electrical-conduit routing difficulties, introduces a different set of difficulties including increased cost and weight and degradation in image quality associated with longer light-transmission lengths and defects attendant to the taper fabrication process.
Accordingly, there exists a need for an imaging module including an optical component with the image-reducing characteristics of a traditional reducer and the relatively thin profile of a traditional optical fiber faceplate.